Al Canton del Vin sells bottled wines, but also a large variety of "sfuso" wines from the Veneto region. Sfuso wines are wines in the barrel that haven't yet been decanted into glass bottles. A litre of sfuso costs between 2 & 3 Euros. So, if you need table wine, cooking wine, or are just curious to taste a variety of wines from the Veneto without spending a fortune, definitely check this place out.
Manuel, the own of Al Canton del Vin, told me that Al Canton absolutely does not sell wines by the glass. As the sign just under the rack of wine glasses indicates: "No Ombre!" This is a matter of permits, so please do not treat Al Canton del Vin as a bar. However, here in Castello we are in the real small town Venezia. I am willing to bet that if I peek my head in at around 7pm this evening a few of the other neighbors will have dropped in for just a few sips!